Various devices for sensing liquid level are known. Most such devices are a part of a switching mechanism for controlling a motor and pump. In addition, most such devices use a float of some kind which starts the motor and pump when the float has risen a predetermined distance and which stops the motor and pump when it subsequently goes down a predetermined distance. Exemplary patents include U.S. Pat. No. 3,316,845, U.S. Pat. No. 3,941,073, U.S. Pat. No. 4,081,639, U.S. Pat. No. 4,186,419 and U.S. Pat. No. 4,345,879.
The float sensor/switches function well, but are relatively expensive and are subject to hanging up and replacement because of various defects inherent in particular designs. The concept, however, has been used for years which is probably the reason why simpler and more reliable mechanisms such as the present invention have not been identified.